Floor panels with edge connectors

ABSTRACT

Floor covering, including hard floor panels which, at least at the edges of two opposite sides, are provided with coupling parts, cooperating which each other, substantially in the form of a tongue and a groove, wherein the coupling parts are provided with integrated mechanical locking elements which prevent the drifting apart of two coupled floor panels in a direction (R) perpendicular to the related edges and parallel to the underside of the coupled floor panels, and provide a snap-action coupling.

RELATED APPLICATION DATA

This application is a continuation of application Ser. No. 11/451,358filed Jun. 13, 2006; which is a continuation of application Ser. No.11/417,189 filed May 4, 2006, now U.S. Pat. No. 7,644,554; which is acontinuation of application Ser. No. 10/256,183 filed Sep. 27, 2002, nowU.S. Pat. No. 7,040,068; which is a continuation of application Ser. No.09/471,014, filed Dec. 23, 1999, now U.S. Pat. No. 6,490,836; which is acontinuation of application Ser. No. 08/872,044 filed Jun. 10, 1997, nowU.S. Pat. No. 6,006,486.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a floor covering made of hard floor panels.

2. Related Technology

In the first instance, the invention is intended for so-called laminatedfloors, but generally it can also be applied for other kinds of floorcovering, consisting of hard floor panels, such as veneer parquet,prefabricated parquet, or other floor panels which can be compared tolaminated flooring.

It is known that such floor panels can be applied in various ways.

According to a first possibility, the floor panels are attached at theunderlying floor, either by glueing or by nailing them on. Thistechnique has a disadvantage that is rather complicated and thatsubsequent changes can only be made by breaking out the floor panels.

According to a second possibility, the floor panels are installedloosely onto the subflooring, whereby the floor panels mutually matchinto each other by means of a tongue and groove coupling, whereby mostlythey are glued together in the tongue and groove, too. The floorobtained in this manner, also called a floating parquet flooring, has asan advantage that it is easy to install and that the complete floorsurface can move which often is convenient in order to receive possibleexpansion and shrinkage phenomena.

A disadvantage with a floor covering of the above-mentioned type, aboveall, if the floor panels are installed loosely onto the subflooring,consists in that during the expansion of the floor and its subsequentshrinkage, the floor panels themselves can drift apart, as a result ofwhich undesired gaps can be formed, for example, if the glue connectionbreaks.

In order to remedy this disadvantage, techniques have already beenthrough of whereby connection elements made of metal are providedbetween the single floor panels in order to keep them together. Suchconnection elements, however, are rather expensive to make and,furthermore, their provision or the installation thereof is atime-consuming occupation.

Examples of embodiments which apply such metal connection elements aredescribed, among others, in the documents WO 94/26999 and WO 93/13280.

Furthermore, couplings are known which allow coupling parts to snap fitinto each other, e.g., from the documents WO 94/1628, WO 96/27719 and WO96/27721. The snapping-together effect obtained with these forms ofembodiment, however, does not guarantee a 100-percent optimumcounteraction against the development of gaps between the floor panels,more particularly, because in fact well-defined plays have to beprovided in order to be sure that the snapping-together is possible.

From GB 424.057, a coupling for parquetry parts is known which, inconsideration of the nature of the coupling, only is appropriate formassive wooden parquetry.

Furthermore, there are also couplings for panels known from thedocuments GB 2.117.813, GB 2,256.023 and DE 3.544.845. These couplings,however, are not appropriate for connecting floor panels.

BRIEF SUMMARY OF THE INVENTION

The invention aims at an improved floor covering of the aforementionedtype, the floor panels of which can be coupled to each other in anoptimum manner and/or the floor panels of which can be manufactured in asmooth manner, and whereby preferably one or more of the aforementioneddisadvantages are excluded.

The invention also aims at a floor covering which has the advantage thatno mistakes during installing, such as gaps and such, can be created.

Furthermore, the invention also aims at a floor covering whereby thesubsequent development of gaps is excluded or at least counteracted inan optimum manner, whereby also the possibility of the penetration ofdirt and humidity is minimalized.

To this aim, the invention relates to a floor covering, consisting ofhard floor panels which, at least at the edges of the two oppositesides, are provided with coupling parts, cooperating which each other,substantially in the form of a tongue and a groove, wherein the couplingparts are provided with integrated mechanical locking elements whichprevent the drifting apart of two coupled floor panels into a directionperpendicular to the related edges and parallel to the underside of thecoupled floor panels. Hereby, these coupling parts are optimalized insuch a manner that they allow that any form of play is counteracted andpreferably is excluded.

By integrated mechanical locking elements is understood that these forma fixed part of the floor panels, either by being connected in a fixedmanner to the floor panels, or by being formed in one piece therewith.

In a first important preferred form of embodiment, the coupling partsare provided with locking elements which, in the engaged position of twoor more of such floor panels, exert a tension force upon each otherwhich force the floor panels towards each other. As a result of thisthat not only the formation of gaps counteracted during installation,but also in a later stage the development of gaps, from any causeswhatsoever, is counteracted.

According to another characteristic of the intention, the couplingparts, hereby are formed in one piece with the core of the floor panels.

According to a second important preferred embodiment, the aforementionedoptimalization is achieved in that the floor covering panel possessesthe following combination of characteristics: the coupling parts andlocking elements are formed in one piece with the core of the floorpanels; the coupling parts have such a shape that two subsequent floorpanels can be engaged into each other exclusively by snapping togetherand/or turning, whereby each subsequent floor panel can be insertedlaterally into the previous; the coupling parts are interlocked freefrom play in all directions in a plane extending perpendicular to theaforementioned edges; the possible difference between the upper andlower lip of the lips which border the aforementioned grooves, measuredin the plane of the floor panel and perpendicular to the longitudinaldirection of the groove, is smaller than one time the total of thethickness of the panel; the total thickness of each related floor panelis larger than or equal to 5 mm; and that the basic material of thefloor panels, of which the aforementioned core and locking elements areformed, consists of a ground product which, by means of a binding agentor by means of melting together, is made into a unitary composite,and/or of a product on the basis of synthetic material and/or of a chipboard with fine chips.

Due to the fact that the coupling parts provide for an interlocking freefrom play, as well as due to the fact that these coupling parts aremanufactured in one piece, from the basic material of the floor panels,a perfect connection between adjacent floor panels can always beguaranteed, even with repeated expansion and shrinkage of the floorsurface.

This combination of characteristics can be combined or not with theaforementioned characteristic that the locking elements exert a tensionforce upon each other when panels are joined together.

According to a third important preferred embodiment, the characteristicsof which may or may not be combined with the characteristics of theembodiments described above, the floor covering is characterized in thatthe lower lip which limits or defines the lower side of the groove,extends beyond the upper lip in the plane of the panel; the lockingelements are formed at least of a contact portion which inwardly slopesdownward; and that this portion, at least partially, is located in theportion of the lower lip which extends beyond the upper lip. Theadvantages of these features will appear from the further description.

According to a preferred form of embodiment, the floor panels areconfigured as elongated panels and the coupling parts described aboveare applied along the longitudinal sides of these panels.

According to a particular form of embodiment, coupling parts areprovided at the other two sides, too, either of another constructionthan described above or not.

In the most preferred form of embodiment, for the basic material useshall be made of the aforementioned product, which, as said, is groundand, by means of a binding agent, made into a unitary compositematerial. More particularly, for the core use shall be made offinely-ground wood which preferably is glued, more particularly,moisture resistant glued. Still more particularly, for the core useshall be made of so-called HDF board (High Density Fibreboard) or MDFboard (Medium Density Fibreboard) which is highly compressed ground woodparticles (fibers) and binder material. Hereinafter, the wood componentof the core material shall be referred to as “wood product”.

The fact that the invention is applied to floor panels the basicmaterial of which consists of the material described above, offers theadvantage that with the processing of this material, very smoothsurfaces are obtained whereby very precise couplings can be realized,which, in first instance, is important in the case of a snap-togetherconnection and/or turning connection free from play. Also, very specialforms of coupling parts can be manufactured in a very simple mannerbecause the aforementioned kinds of material can be processedparticularly easy.

The surfaces obtained with HDF and MDF also have the advantage that thefloor panels mutually can be shifted readily alongside each other ininterlocked condition, even when engaged with a tensioning force.

The applicants also discovered that the aforementioned materials, inparticular HDF and MDF, show ideal features in order to realize aconnection, such as mentioned above, as these material show the rightfeatures in respect to elastic deformation in order to, on the one hand,realize a snap-together effect, and, on the other hand, receiveexpansion and shrinkage forces in an elastic manner, whereby it isavoided that the floor panels come unlocked or are damaged in anirreparable manner.

In the case that for the core use is made of a material based onsynthetic material, to this end solid synthetic material can be used aswell as a mixture of synthetic materials, eventually composed ofrecycled materials.

The floor covering preferably is formed by joining the floor panels intoeach other free of glue. Hereby, the connections are of such nature thatthe floor panels can be disassembled without being damaged, such that,for example, when moving from one residence or location to another, theycan be taken along in order to be placed down again. It is, however,clear that a glueing between tongue and groove is not excluded.

The invention, of course, also relates to floor panels which allow therealization of the aforementioned floor covering.

The invention also relates to a method for the manufacturing of theaforementioned floor panels with the advantage that the tongues and/orgrooves, including the corresponding locking means, can be provided atthe floor panels at high production speeds without problems. Moreparticularly, it aims at a method which allows that the rathercomplicated forms of the tongue and the groove of the aforementionedfloor panels can be formed completely by means of milling cutters, thediameter of which can be chosen independent of the form to be realized,such that the use of small milling cutters, for example finger cutters,with diameters smaller than the depth of the tongue or groove can beexcluded.

In accordance with this method the tongue and/or groove is formed bymeans of a milling process using at least two sequential milling cyclesor passes by means of milling cutters which are positioned at differentangles in respect to the related floor panel. During each of theaforementioned milling cycles, preferably substantially the final formof one flank, either of the tongue or of the groove, is formed.

For the aforementioned two milling cycles, thus, milling cutters areused which extend outside the groove, respectively the tongue. Moreparticularly the diameters of these milling cutters shall at least be 5times and even better 20 times larger than the thickness of the floorpanels.

The use of milling cutters having the aforementioned diameters has as anadvantage that the normal production speeds can be maintained which arealso applied during milling of a classical straight tongue and groove.There is also the advantage obtained that the installation of suchmilling cutters induce only minor or no additional costs because suchmilling cutters can be placed directly upon a motor shaft and/or theconventional machines can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

With the intention of better showing the characteristics according tothe invention, in the following, as an example without any limitativecharacter, several preferred forms of embodiment are described, withreference to the accompanying drawings, wherein:

FIG. 1 represents a floor panel of a floor covering according to theinvention;

FIG. 2, on a larger scale, represents a cross-section according to lineII-II in FIG. 1;

FIGS. 3 and 4 represent how two floor panels with coupling partsaccording to FIG. 2 match into each other;

FIG. 5, on a larger scale, represents a cross-section according to lineV-V in FIG. 1;

FIGS. 6 and 7 represent how two floor panels with coupling partsaccording to FIG. 5 match into each other;

FIGS. 8 to 11 represent a number of variants of coupling parts of floorpanels according to the invention;

FIG. 12 schematically represents how the floor parts can be providedwith coupling parts;

FIG. 13 represents a cross-section according to line XIII-XIII in FIG.12;

FIGS. 14 to 21, on a larger scale and in cross-section, represent thepenetration of the milling cutters which are indicated in FIG. 12 witharrows F14 to F21;

FIG. 22 represents a floor panel according to the invention;

FIG. 23, on a larger scale, represents the coupling of two floor panelsof FIG. 22;

FIGS. 24 and 25 represent two manners of coupling floor panels accordingto FIG. 22 to each other.

DETAILED DESCRIPTION

The invention relates to a floor covering which is composed of hardfloor panels 1, for example, such as a laminated panel as shown in FIG.1.

These floor panels 1 can be of various shape, for example, elongated orsquare, or of any other shape having linear side edges intersecting atright angles (rectangular).

In the most preferred form of embodiment, they shall be manufactured inan elongated form, such as shown in FIG. 1, for example, with a lengthof 1 to 2 meters. The thickness, however, can also vary, but ispreferably 0.5 to 1.5 cm, and more particularly 0.8 cm.

Each floor panel 1 is, at least at the edges of two opposite sides 2-3,provided with tongue and groove coupling parts 4-5 which permit twoadjacent identical floor panels 1 to be coupled to each other.

According to the invention, the coupling parts 4-5, as represented inthe FIGS. 2 to 4, are provided with integrated mechanical locking partsor locking elements 6 which prevent the drifting or sliding apart of twocoupled floor panels 1 in a direction D perpendicular to the respectivesides 2-3 and parallel to the underside 7 of the coupled floor panels 1;the coupling parts 4-5 and the locking elements 6 are formed in onepiece with the core 8 of the floor panels 1; the coupling parts 4-5 havesuch a shape that two subsequent floor panels 1 can be engaged into eachother solely by snapping-together and/or turning after the couplingparts are partially engaged, whereby each subsequent floor panel 1 canbe laterally inserted into the previous; and the coupling parts 4-5preferably are interlocked free from play in all directions in a planewhich is located perpendicular to the aforementioned edges.

In the case of floor panels 1 with an elongated shape, as represented inFIG. 1, the respective coupling parts 4-5 are located at thelongitudinal sides 2-3.

The coupling parts 4-5 can be realized in various forms, although thebasic forms thereof will always be formed by a tongue 9 and a groove 10.

In the form of embodiment of FIGS. 2 to 4, the related floor panel 1 isprovided with tongue and groove coupling parts 4-5 and locking means orlocking elements 6 which allow the coupling parts of two floor panels 1to be mutually engaged by means of a turning movement, without theoccurrence of any snap-together effect.

In the represented example, the locking elements 6 consist of a firstlocking element 11, formed by a protrusion with a bent round shape atthe lower side 12 of the tongue 9, and a second locking element 13(shown in FIG. 2), formed by a recess with a bent hollow upwardly facingor downwardly concave shape in the upper side of lower wall 14 of thelower lip of the groove 10.

The locking elements 11-13 ensure that two floor panels 1 which arecoupled to each other can not move laterally in the horizontal planewith respect to each other.

In order to enable two floor panels 1 to be inserted into each other bymeans of a turning movement, the curvatures preferably are circular. Thebottom side 12 of locking means or locking elements 6 has a curvaturewith a radius R1, the center of which coincides with the respectiveupper side edge 15 of the floor panel 1, whereas the upper side of thelower lip of the groove locking part 5 has a curvature with a radius R2which is equal to the radius R1, but its center coincides with therespective upper edge 16. Radii R1 and R2 may also be applied which arelarger or smaller than the distance to the upper side edges 15, 16respectively, and/or which differ from each other in size.

The upper side 17 of the tongue 9 (called an upper tongue contactsurface) and the lower side of upper wall or side 18 of the upper lipgroove 10 are preferably flat and preferably are located in thehorizontal plane.

The inner side 20 of the groove 10 and the front side 19 of the tongue 9of the two interlocked floor panels 1 preferably do not fit closelyagainst each other, such that an intermediate space 21 is createdbetween them into which possible dust remainders or such can be pushedaway by means of the tongue 9.

The tongue 9 and the groove 10 preferably have shapes which arecomplementary to each other, such that the upper side 17 of tongue 9 inthe engaged condition of two identical floor panels 1 precisely sitsagainst the upper lip lower side 18 and the lower wall 14 of the lowerlip of the groove 10, whereby a pressure P, exerted against the upperlip 22, is received or reacted not only by this lip 22, but by thecomplete structure, because this pressure can be transmitted through thetongue 9 and the lower lip 23 to cause the panels to be urged towardseach other.

It is, however, clear that a number of minor deviations to thesecomplementary forms can occur which, anyhow, have no or almost no effectupon the receipt and transmission of pressure forces. For example, achamfer 24 on lip 22 and a recess 25 can be provided, as represented inFIGS. 2 to 4, as a result of which the subsequent floor panels 1 caneasily be pushed and guided into each other, such that no possibleridges in the subflooring or such render good insertion difficult.

As represented in the FIGS. 5 to 7, the floor panels 1 according to theinvention can also, along the sides 26-27 which are at a right angle tothe sides 2-3, be provided with coupling parts 28-29 which have lockingelements 30, too. The coupling parts 28-29 are preferably also realizedin the shape of a tongue 31 and a groove 32. Hereby, the lockingelements 30 do not have to be of the same nature as the locking elements6.

Preferably, at the sides 26-27 locking elements are provided which allowfor an engagement and interlocking by means of a lateral translationmovement in direction T only, as represented in FIGS. 6 and 7. To thisaim, the locking elements 30 consist of a snap-together connection withlocking elements 33 and 34 which grip behind each other.

As represented in FIGS. 5 to 7, the locking element 33 preferablyconsists of a downwardly extending protrusion of the lower side 35 ofthe tongue 31 which can be located in an upwardly facing recess 36 in alower lip 43 extending distally from the inner side of the groove 32.The locking element 34 is formed by the upward directed part orprotrusion which defines the distally outer end of recess 36.

In this case, the locking elements 33-34 have contact or lockingsurfaces 38-39 which are parallel to each other and preferably extend inan obliquely inclined manner, according to a direction which simplifiesthe snapping-together of the panels, as illustrated. The common line orplane of tangency L which is determined by the common tangent at themeeting point or area of surfaces 38-39, hereby forms an angle A slopinginwardly and downwardly from an outer region to an inner region relativeto the underside 7 of the panel having the groove coupling part, whichangle is smaller than 90°.

The locking elements 33-34 preferably are provided with inclinedportions 40 and 41 extending downwardly and proximally from a distalzone to a proximal zone on the tongue element and downwardly anddistally from a proximal towards a distal zone on the lower lip of thegroove, which, when two floor panels 1 are engaged, cooperate with eachother in such a manner that the locking elements 33-34 can easily bepushed over each other until they grip behind each other at theirlocking surfaces by means of a snap-together effect (FIGS. 6 and 7).

The thickness W1 of the tongue 31 preferably is equal to the width W2 ofthe groove 32, such that compression pressure P applied to the upper lip42 is reacted by the tongue 31 which, in its turn, then is reacted bythe lower lip 43.

Analogous to the chamfer 24 and recess 25, a recess 44 and a chamfer 45are provided also at the edges 28-29.

It is noted that such a snap-together coupling can also be applied atthe edges 2-3. Hereby, this can be a snap-together coupling analogous tothese of FIGS. 5 to 7, but this can also be a snap-together couplingusing other forms of coupling configurations, for example, such asrepresented in FIGS. 8 and 9. Contrary to the locking elements 33-34which consist of rather local protrusions, in the forms of embodiment ofFIGS. 8 and 9 use is made of locking elements 46-47 which, in comparisonto the total width B of the coupling, extend over a rather largedistance.

In this case, the locking elements 46-47 are also provided at the lowerside 12 of the tongue 9 and the upper side of the wall 14 of the lowerlip of groove 10.

According to FIG. 8, the locking elements 46-47 have locking surfaces48-49 which are at an angle with the plane of the floor panel 1. In thismanner, a coupling is obtained which is interlocked in a particularlyfixed manner.

As represented in FIG. 9, the locking elements 46-47 possibly can beconfigured in such a manner that substantially only a linear contact atthe locking surfaces is obtained, for example, because the lockingsurfaces directed towards each other are formed with differentcurvatures.

The locking surfaces, directed towards each other, of the lockingelements 46-47 according to FIG. 9 hereby consist of curved surfaces.The common line or plane of tangency L forms an angle A which is smallerthan 90°, and more preferably is smaller than 70°.

In this manner, the locking element 46 preferably has two portions witha different curvature, on one hand, a portion 50 with a strong curvatureand, on the other hand, a portion 51 with a weak curvature. The portion50 with the strong curvature provides for the formation of a firmcoupling. The portion 51 with the weak curvature facilitates thecoupling parts 4-5 to be brought into each other easily. Theintermediate space (shown at Z1 in FIG. 8) forms a chamber which offersspace for dust and the like which, when engaging two floor panes 1,inevitably infiltrates there.

In the case of a snap-together connection, for example, a connectionsuch as represented in FIGS. 7 to 9, preferably the tongue 9-31 has ashape that thickens from below, which then can cooperate with a widenedportion in the groove 10, the lower lip of which likewise varies inthickness, as shown.

In FIG. 10, a variant is represented whereby at least at the level ofthe upper side edges 15-16, a sealing material 52 is provided, as aresult of which a watertight sealing can be assured. This sealingmaterial 52 may consist of a strip or covering which is providedpreviously at the floor panel 1, either at one or both upper side edges15-16.

In FIG. 11, a further variant is represented, whereby the lockingelement 6 is formed by an upward directed portion 53 at the tongue 9,which as a result of a turning movement of the panel, is brought behinda downward-directed portion 54 on the upper wall 18. More particularly,this is obtained by forming the upper side 17 and the upper wall 18 witha curvature R3, the center of which is situated at the upper side edges15-16, and forming the tongue lower side 12 and the wall 14 of lower lip23 with a radius R4, the center of which is also situated at the upperside edges 15 and 16, respectively. These radii R3-R4 can be chosenotherwise, too.

In general, according to the invention, the difference between, on onehand, the radius R1, R3 respectively, and, on the other hand, the radiusR2, R4 respectively, preferably should not be larger than 2 mm.

It is also preferred that the center of these radii be situated insidethe circle C1, C2 (see FIG. 2) respectively, which extends with a radiusR5 of 3 mm centered at upper side edge 15, 16 respectively.

Finally is noted that, according to the invention, the lower lip 23-43,as represented in FIGS. 2 to 7, can be formed distally longer than theupper lip 22-42 possibly with the recesses of the locking elementsextending partially under the upper lip and preferably, where the lowerlip is longer than the upper lip, with the lower lip locking surfacelocated beyond the upper lip. This has an advantage that the couplingparts 4-5-28-29 can be shaped in an easier manner by means of a millingcutter or the like. Furthermore, this simplifies the engagement of twofloor panels 1, because each subsequent floor panel 1 duringinstallation can be placed upon the protruding lower lip 23-43, as aresult of which the tongue 9-31 and the groove 10-32 automatically arepositioned in front of each other.

The embodiments wherein the lower lip 23 is equal to or distally shorterthan the upper lip 22, in their turn, offer the advantage that noprotruding lip 23 remains at the extreme edge of the floor which mightcause problems in finishing the floor installation.

In order to allow for a smooth assembly, to guarantee the necessarystability and firmness and in order to limit the quantity of material tobe cut away, the difference E between the distally outer edge of theupper lip 22-42 and the distally outer edge of the lower lip 23-43,measured in the plane of the floor panel and perpendicular to thelongitudinal direction of the groove 10, should preferably be keptsmaller than one time the total thickness F of the floor panel 1. Forstability's sake, normally this total thickness F shall never be lessthan 5 mm.

The small dimension of the difference E offers the advantage that thelower lip need not be strengthened by a reinforcement strip or the like.

According to a particular form of embodiment, the central line M1through the tongue 9 and the groove 10 is situated lower than the centerline M2 of the floor panel 1, such, that the upper lip 22-42 is thickerthan the lower lip 23-43. In first instance, this is essential in thiskind of connection, because then it is the lower lip 23-43 which bends,whereby the upper side of the floor panel 1 is kept free of possibledeformations.

As explained in the introduction, for the core 8 a material is chosenfrom the following series:

-   -   a ground product which, by means of a binding agent or by means        of melting together is made into a unitary composite material;    -   a product based on synthetic material;    -   chip board with fine chips.

The invention shows its usefulness, in first instance, preferably withlaminated flooring, due to the reasons explained in the introduction.

As represented in the examples of the FIGS. 2 to 11, such laminatedflooring preferably consists of a core 8 made of MDF medium densityfiberboard board, HDF high density fiberboard board or similar, wherebyat least at the upper side of this core 8 one or more layers of materialare provided.

More particularly, it is preferred that the laminated flooring isprovided with a decorative layer 55 and a protective top layer 56. Thedecorative layer 55 is a layer, impregnated with resin, for example,made of paper, which can be imprinted with a variety of patterns, suchas a wood pattern, a pattern in the form of stone, cork, or similar oreven with a fancy pattern. The protective top layer 56 preferably alsoconsists of a layer saturated with resin, for example, melamine resin,which in the final product is transparent.

It is clear that still other layers can be applied, such as anintermediate layer 57 upon which the decorative layer 55 is provided.

Preferably, also a backing layer 58 shall be applied at the underside 7,forming a counterbalancing element for the top layers and, thus,guaranteeing the stability of the form of the floor panel 1. Thisbacking layer 58 may consist of a material, for example paper,impregnated with a resin, for example, a melamine resin.

As represented schematically in FIG. 12, the tongue 9 and the groove 10,and preferably also the tongue 31 and the groove 32 are formed by meansof a milling process. In the case that a profile has to be applied onall four sides, the floor panels 1 preferably shall be displaced bymeans of two sequential perpendicular movements V1 and V2, wherebyduring the first movement profiles at two opposite edges are provided,in this case the longitudinal edges, by means of milling devices 59-60,whereas during the second movement profiles are provided at the otheredges, in this case the small edges, by means of milling devices 61-62.During these processing, the floor panels 1 preferably are put withtheir decorative layer directed downward.

According to an important characteristic of the invention, eachrespective tongue 9-31 and groove 10-32 are formed by means of a millingprocess with at least two sequential milling cycles or passes by meansof milling cutters which are positioned at different angles in referenceto the related floor panel 1.

This is illustrated in FIGS. 13, 14 and 15, wherein it is representedhow a groove 10 is realized by means of two milling cycles by means oftwo milling cutters 63 and 64. FIGS. 16 and 17 represent how the tongue9 is shaped by means of milling cutters 65 and 66.

The FIGS. 18-19 and 20-21 represent similar views showing how the groove32 and the tongue 31 are shaped by means of milling cutters 67-68 and69-70, positioned at an angle.

During each of the aforementioned milling passes, substantially thefinal shape of one flank is fully realized. For example, the millingcutter 63 of FIG. 14 determines the final shape of the lower flank 71 ofthe groove 10, whereas the milling cutter 64 determines the final shapeof the upper flank 72.

As mentioned in the introduction, preferably milling cutters 63 to 72shall be used, having diameters G which are at least 5 times, and evenbetter at least 20 times larger than the thickness F of the floor panels1.

Apart of the mentioned milling cutters, preferably still other millingcutters are applied, for example, in order to remove a part of thematerial to be removed during a first premachining cycle.

In the FIGS. 22 to 25, a particularly preferred form of embodiment of afloor panel 1 according to the invention is represented. Hereby, theparts which correspond with the previous embodiments are indicated withcorresponding references.

An important characteristic herein consists in that the coupling parts4-5 are provided with locking elements 6 which, in engaged conditionwith the panels in a common plane, exert a tension force upon eachother, as a result of which the engaged floor panels 1 are forcedtowards each other in compression. As represented, this is realizedpreferably by providing the coupling parts with an elastically yieldableor bendable portion, in this case the lower lip 43, which, in engagedcondition, is at least partially bent and in this way creates a tensionforce which results in the engaged floor panels 1 being forced towardseach other. The resultant bending V, as well as the tension force K, areindicated in the enlargement view of FIG. 23.

In order to obtain the tension force K pressing together the engagedfloor panels 1, the bendable portion, in this case the lower lip 43,preferably is provided, as represented, with a proximally facinginwardly and downwardly inclined locking surface 73 which preferably cancooperate with a corresponding proximally facing (relative to thetongue) locking surface 74 on tongue 9. These locking surfaces 73-74 aresimilar to the aforementioned locking surfaces 39-38 and also similar tothe inclined portions of the lower lip of FIGS. 2 to 4.

In the FIGS. 2 and 5, the locking elements form complementary matchingshapes; it is, however, clear that, by a modification, also a tensioneffect similar to that shown in FIG. 23 can be realized.

Due to, on one hand, the contact between the locking surfaces along theangle A, and, on the other hand, the fact that a tension force K iscreated, a compression force component K1 is produced, as a result ofwhich the floor panels 1 are drawn against each other in compression.

Preferably, the angle A of the mutual line or plane of tangency ofcontact surfaces 73-74 relative to the principal horizontal plane of thepanel is situated between 30 and 70 degrees. In the case that use ismade of the embodiment whereby a tension force K is realized, an angle Aof 30 to 70 degrees is ideal in order, on one hand, to effect an optimumpressing-together of the floor panels 1 at their adjoining upper sideedges and, on the other hand, to ensure that the floor panels 1 caneasily be engaged and respectively disassembled.

Although the pressing or compression force component K1 preferably isdelivered by the aforementioned lower lip 43, the invention does notexclude other forms of locking elements or structures whereby this forceis delivered by other bendable portions.

It is noted that the bending V is relatively small, for example, severalhundredths up to several tenths of a millimeter, and does not have aninfluence upon the placement of the floor covering. Furthermore itshould be noted that such floor covering generally is placed upon anunderlayer (not shown) which is elastically compressible, as a result ofwhich the bending V of the lip 43 only produces local bending of theunderlayer.

Due to the fact that the lip 43 is bent apart and that it remainssomewhat bent apart in engaged position, the additional advantage isobtained that, when exerting a pressure upon the floor covering, forexample, when placing an object thereupon, the pressing-togethercompressive force is enhanced and, thus, the development of undesiredgaps between adjoining upper side edges is counteracted even more.

It is noted that the inventors have found that, contrary to allexpectations, an ideal tension force can be realized by manufacturingthe coupling parts 4-5, including the locking elements 33-34, andpreferably the complete core 8, of HDF board or MDF board, althoughthese material normally only allow a minor elastic deformation.

HDF and MDF also offer the advantage that smooth surfaces are obtained,as a result of which the locking elements can be moved easily over eachother.

According to a variant of the invention, the tension force can also besupplied by means of an elastic compression of the material of thecoupling parts themselves, to which end these coupling parts, andpreferably the complete core 8, would be manufactured using anelastically compressible material.

A further particular characteristic of the embodiment of FIGS. 22 to 25consists in that the floor panels 1 can be selectively engaged by meansof a turning or angling-in movement, as represented in FIG. 24, as wellas by means of laterally shifting them towards each other insubstantially a common plane, as represented in FIG. 25, preferably insuch a manner that, during the engagement by means of the turningmovement with the coupling parts partially engaged, a maximum bending Vmresults in the coupling parts, more particularly in the lip 43, whichbending Vm is less pronounced, if not nonexistent, as in the FIGS. 2 to4, in comparison to the bending Vm which results when the floor panels 1are engaged by means of shifting them towards each other, as in FIG. 15.

The advantage of this consists in that the floor panels 1 can be engagedeasily by means of a turning movement, without necessitating use of atool therefore, whereas it still remains possible to engage the floorpanels also by means of shifting them laterally. This latter is useful,in first instance, when the last panel has to be placed partially undera door frame or similar situation. In this case, the floor panel 1 canbe pushed under the door frame with the side which does not have to beengaged and subsequently, possibly by means of tools, can be snappedinto the adjacent floor panel by lateral sliding together.

It is noted that the shapes of the coupling parts 4-5 shown in FIGS. 22to 25 can also be used for the coupling parts 28-29 of the short sidesof the panels.

According to the invention, in the case that the four sides 2-3-26-27are provided with coupling parts 4-5-28-29, these coupling parts can beformed in such a manner that in one direction a firmer engagement thanin the other direction is effected. In the case of elongated floorpanels 1, for example, such as represented in FIG. 1, the locking at thesmall sides 26-27 preferably shall be more pronounced than at thelongitudinal sides 2-3. The length of the parts at the small sides,namely, is smaller and, in principle, less firm. This is compensated forby providing a more pronounced locking.

This difference in engagement can be obtained by shaping the contactsurfaces 73-74 with different angles.

Preferably, the aforementioned protrusion, more particularly the lockingelement 33, is bounded by at least two portions 75-76 (shown in FIG.22), respectively a proximal portion 75 with a strong (steep) downwardinclination from an upper proximal area to a lower distal area whichprovides for the locking, and a distal portion 76 with a weaker (lessinclined) downward inclination from an upper distal area to a lowerproximal area which renders the engagement or guidance of the couplingparts easier. In the embodiment of FIGS. 22 to 25, these portions 75-76extend in straight planes, but, as already described with reference toFIG. 9, use can also be made of curved portions 50-51. In FIG. 5, theseare the locking surface 38 and the distal inclined portion 40.

In the preferred form of the invention, the floor panels 1 comprisecoupling parts 4-5 and/or 28-29 exhibiting one of the following or thecombination of two or more of the following features:

-   -   a curvature 77 (shown in FIG. 22) at the lower side of the        tongue 9 and/or a curvature 78 at the lower lip 43 which form a        guidance when turning two floor panels 1 into each other, with        the advantage that the floor panels 1 can be engaged into each        other easily during installation;    -   roundings 79-80 at the intersection of surfaces 74 and 75 on the        tongue and on the upper edge of the locking element, with the        advantages that the locking elements 33-34 can easily shift over        each other during their engagement, or during disassembly of the        floor panels 1 and that the locking elements will not be        damaged, for example, crumble away at their edges, even if the        floor panels are engaged and disassembled;    -   dust chambers 81, or spaces 21 as in FIGS. 4 and 23, between all        sides, directed laterally towards each other, of the engaged        floor panels 1, with the advantage that inclusions which get        between the floor panels 1 during the engagement do not exert an        adverse influence upon good engagement;    -   a shaping of the tongue 9 which is such, for example, by the        presence of a chamfer 82, that the upper side of the tongue 9        becomes situated from the first joining together or substantial        contact of the panels, under the lower side of the upper lip 42        when the floor panels 1 are pushed towards each other in        substantially the same plane, as indicated in FIG. 25, with the        advantage that the front or distal extremity or end of the        tongue 9 does not press against the front side of the upper lip        42 or the front edge of the bottom lip 43 when the floor panels        are pushed towards each other in the same plane;    -   a ramp surface 83, hereinbefore also called inclined portion 41,        formed at the distally outer end of the lower lip 43, with the        advantage that the locking elements 33-34 shift smoothly over        each other and that the lower lip 43 is bent uniformly;    -   in the engagement direction only one important contact point        which is formed by a section 84 at the location of the upper        side edges of the floor panels 1, with the advantage that the        aforementioned tension force is optimally transferred to the        upper side of the floor panels 1 and that the development of        openings between the floor panels 1 is counteracted;    -   contact surfaces 85-86, more particularly abutment surfaces,        formed by the upper side of the tongue 9 and the upper side of        the groove 10 (or more precisely the lower side of the upper lip        of the groove) which, over the largest portion of their length,        are flat and run parallel to the plane which is defined by the        floor panels 1, as well as lower tongue and groove contact        surfaces cooperating with each other, formed by curvatures        77-78, with the advantage that no mutual displacement in height        between two engaged floor panels 1 is possible, even if the        insertion depth of the tongue 9 into the groove 10 should vary        due to various causes; in other words, no height differences may        occur between the adjacent floor panels.

In the embodiment of FIGS. 22 to 25, all these characteristics arecombined; it is, however, clear that, as becomes evident from FIGS. 2 to11, these features can also be provided separately or in a limitedcombination with one another.

As becomes evident from FIGS. 5 to 7 and 22 to 25, an importantcharacteristic of the preferred embodiment of the invention consists inthat the cooperative locking element 6, in other words, the portionproviding for the snap-together and engagement effect, are situated inthat portion of the lower lip 23-43 which extends beyond the distal edgeof the upper lip 22-42, more particularly, the lowermost point 87 of thelocking part (i.e., protrusion) 33 is situated under the top layer ofthe floor panel 1. For clarity's sake, this top layer is indicated inthe FIGS. 22-25 only as a single layer.

It should be noted that the combination of features, the lower lip 23-43extending further than the upper lip 22-42; the lower lip lockingelements 6 being formed at least by means of a locking surface whichinwardly slopes downward relative to the lower lip, and wherein thislocking surface, at least partially, is located in the portion of thelower lip 23-43 which lies distally beyond the upper lip 22-42, isparticularly advantageous, among others, in comparison with thecouplings for floor panels described in the documents WO 94/01628, WO94/26999, WO 96/27719 and WO 96/27721. The sloping locking surfaces havethe advantage that the floor panels 1 can be disassembled again. Thefact that this sloping portion is situated in the extended portion ofthe lower lip 23-43 adds the advantage that no deformations can occurduring coupling which manifest themselves up to the top layer.

According to a preferred characteristic of the invention, theaforementioned locking surfaces 39 or 73, preferably extend in such amanner that the distance between the upper edge 16 of the panel to thelocking surface 39, 73 diminishes between the proximal and distal endsof the sloping locking surface 39, 73, in other words, such that, asrepresented in FIG. 22, the distance X2 is smaller than the distance X1.This is also the case in FIG. 7. This geometry results in the lockingsurfaces 39 and 73 of the recess 36 contacting and passing over thelocking surfaces 38 and 74 of the tongue locking element 30, 33.

Still preferably, this portion only starts at a clear distance E1 (FIG.22) from the outer edge of upper lip 42.

It is obvious that the coupling parts 22 to 25 can also be shaped bymeans of said milling process.

According to a particular characteristic of the invention, the floorpanels 1 are treated at their sides 2-3 and/or 26-27 with a surfacedensifying agent, more particularly a surface hardening agent, whichpreferably is chosen from the following series of products: impregnationagents, pore-sealing agents, lacquers, resins, oils, paraffins and thelike.

In FIG. 22, such impregnation 88 is represented schematically. Thistreatment can be performed over the complete surface of the sides 2-3and/or 26-27 or only over specific portions hereof, for exampleexclusively on the surfaces of the tongue 9 and the groove 10.

The treatment with a surface densifying agent offers, in combinationwith the snap-together effect, the advantage that in various aspectsbetter coupling characteristics are obtained. As a result of this, thecoupling parts 4-5 and/or 28-29 better keep their shape and strength,even if the floor panels 1 are engaged and disassembled repeatedly. Inparticular, if the core 8 is made of HDF, MDF or similar materials, bymeans of this treatment a better quality of surface condition isobtained, such that no abrasion of material occurs during engaging, orduring disassembling.

This treatment also offers the advantage that, at least in the case of asurface hardening, the aforementioned elastic tensioning effect isenhanced.

The present invention is in no way limited to the forms of embodimentdescribed by way of example and represented in the figures, however,such floor covering and the pertaining floor panels 1 can be embodied invarious forms and dimensions without departing from the scope of theinvention.

For example, the various characteristics which are described by means ofthe represented embodiments or examples may be selectively combined witheach other.

Furthermore, all embodiments of coupling elements described before canbe applied at the longer side as well as at the shorter side of a panel.

1. A coupling system for joining panels, which panels are rectangular,i.e. elongated or square, and which comprise a core, said corecomprising a material selected from the group consisting of mediumdensity fibreboard (MDF) and high density fibre board (HDF); said panelscomprising a decorative side, a back side opposite from the decorativeside, a first pair of opposite side edges and a second pair of oppositeside edges; said coupling system comprising cooperating coupling partsprovided at said first pair of opposite side edges enabling two of thepanels to be coupled to each other; wherein the coupling parts aresubstantially in the form of a tongue and a groove, said tongue andgroove comprising an integral extension of said core material; saidgroove closest to said decorative side being bordered by a first liphaving a distal end and said groove closest to said back side beingbordered by a second lip, said second lip also having a distal end, saidsecond lip extending beyond said distal end of the first lip; whereinthe coupling parts are provided with integrated second lip and tonguemechanical locking elements which prevent unrestrained drifting apart oftwo coupled panels in a direction perpendicular to the related sideedges and parallel to a plane including the coupled panels; said secondlip and tongue locking elements defining contact surfaces, respectivelyat said second lip and said tongue, comprising second lip and tonguelocking surfaces which in a coupled condition of two of such panelsprevent said unrestrained drifting apart of the panels; said second liplocking surface being located beyond the distal end of said first lip;wherein said first lip is free of locking surfaces acting in the planeincluding two coupled panels; wherein the coupling parts and lockingelements enable two of such panels to be joined by means of a relativeturning movement of one panel relative to the other panel along adjacentedges to be coupled; wherein said coupling parts and locking elementsare configured such that in the coupled condition of two of such panelsat least two intermediate spaces exist between the coupled side edges,including a first intermediate space and a second intermediate space;said first intermediate space being located between the deepest point ofthe groove and the distal end of the tongue and extending at leastpartly between the second lip and the tongue; and said secondintermediate space being located between the distal end of the secondlip of one of the coupled panels and a wall portion of the other of thecoupled panels that is located in front of said distal end.
 2. Thecoupling system of claim 1, wherein the length with which the second lipextends beyond the first lip, measured in the plane of the panel, issmaller than the thickness of the panel.
 3. The coupling system of claim1, wherein said contact surfaces are configured so that a tangent linewhich is defined by said contact surfaces forms an angle with a plane ofthe coupled panels which is smaller than 90 degrees.
 4. The couplingsystem of claim 1, wherein said contact surfaces are planar.
 5. Thecoupling system of claim 1, wherein said second lip is provided with arecess, said recess being bordered distally by the locking portion ofthe lower lip and wherein said groove, proximally from said recess,comprises a distinctly formed actual wall portion of the groove.
 6. Thecoupling system of claim 1, wherein the coupling parts and lockingelements comprise cut profiles.
 7. The coupling system of claim 1,wherein said locking element at the tongue comprises a protrusion whichcooperates with a recess in the second lip.